In 2017, Hurricane Harvey inundated Houston, Texas, causing many to lose their lives, property and faith in their emergency response services. A little more than a year later, towns across the Southern part of the United States experienced untold devastation; first from Hurricane Florence, then from Hurricane Michael. The frequency and severity of hurricanes and their profound effect on communities cannot not be disentangled from the wider pattern of warming that is changing our planet. The new reality is that extreme weather events will become more common and will require new levels of data-driven preparations. This week, our data integration engineer Eneli Toodu uses the NOAA OISST and the Planet OS Datahub API to derive a comparison between Hurricane Michael and Hurricane Florence.
Hurricane is a classification of tropical storm above 78 miles an hour and is measured categorically from one to five–one being the least intense, five being the most. At their peaks, both Hurricane Florence and Michael registered at Category 4 with top speeds of 144 MPH and 155 MPH, respectively.
Many factors contribute to the magnitude of a hurricane, but sea surface temperature is among one of the most important. Subject to increases in surrounding global temperatures, seemingly minor variations in sea surface temperature can have a large impact on the severity and behavior of a hurricane. LuAnn Dahlman and Rebecca Lindsey of NOAA explain why in their August 2018 paper addressing Oceanic Heat Content. They state, “increasing concentrations of greenhouse gases are preventing heat radiated from Earth’s surface from escaping into space as freely as it used to; most of the excess heat is being stored in the upper ocean. As a result, upper ocean heat content has increased significantly over the past two decades.” Kevin Trenberth, of the National Center for Atmospheric Research (NCAR), goes further to explain how this relates to hurricanes in his paper published in early 2018. “The implication is that the warmer oceans [increase] the risk of greater hurricane intensity and duration. While we often think of hurricanes as atmospheric phenomena, it’s clear that the oceans play a critical role and will shape future storms as the climate changes.”
Examining Florence and Michael
The above GIF captures the sea surface temperature anomalies (departure from a long-term average) as Hurricane Michael moved through the Gulf of Mexico. We can see that sea surface temperature is typically warmer than usual during the storms development. In the area where the hurricane strengthened to a Category 4, the sea surface temperature was almost 3°C warmer than usual.
These findings different slightly from Hurricane Florence. As Florence formed, there were periods where the temperature dipped below the normal average. However, we can see that there were definitely also warmer periods where water, agitated by hurricane winds, became colder after the hurricane passed. Overall, the sea surface temperature was much warmer than normal in most of the places in the Atlantic.
Another interesting aspect of our comparison centered around duration. Hurricane Michael formed on October 7th and made landfall on October 10th. In contrast, Hurricane Florence formed on August 31st and made landfall on September 14th, active for almost 15 days prior to making landfall.
One more thing to note is how the amount of precipitation differed greatly between the two hurricanes. In the GIF above, we can see Hurricane Florence’s path during a six hour window. The maximum amount of precipitation during this period was 118 mm, which is A LOT. For the same sample period Hurricane Michael saw a precipitation maximum of 67mm. This may be largely due to the speed at which Michael travelled–the precipitation was less intense because it poured over a larger area. Florence, by contrast, was more static and drenched a smaller area. We can also see that during Florence, it rained over a longer period while precipitation during Michael lasted for a shorter albeit, more intense duration.
While these findings may not be enough to substantiate formal decision making; it is findings like these, taken in context with additional data, that can contribute to the decisions that underpin effective hurricane preparation. The PlanetOS Datahub makes access and layering of important weather data assets seamless, saving time and eliminating the need for complicated data normalization. From homeowners, to builders to insurance companies, to government agencies, assessing the risk of climate change and building it into preparation for the future is imperative. After all, William Nordhaus just won the Nobel Prize “for integrating climate change into long-run macroeconomic analysis.” It’s past time for us all to start doing the same.
Many of the datasets made available through the Planet OS Datahub have been at the request of our users. For those who require a consolidated, easy to use, resource for accessing large and complex material that the the datahub does not already offer, please reach out to the team and we will work toward bringing it onboard. For more information check out the Planet OS Datahub.